Sefer HaChinuch ספר החינוך

The commandment to prepare six cities of refuge: To separate six cities of refuge from the cities of the Levites, that they should be designated for the one that slays a soul inadvertently to flee there; to fix and straighten the roads that correspond to the cities — and like the matter that they, may their memory be blessed, said (Makkot 10b) that they would write [signs] at the crossroads [saying], “refuge, refuge”; and clear the paths, so that there not be anything on them to delay the fugitive from his run. And about this is it stated (Deuteronomy 19:3), “You shall prepare the path for yourself and divide the border of your Land into three, etc.”

The root of this commandment is well-known and clear — that it be so that the inadvertent killer not be killed by the blood avengers.

From the laws of the commandment is that which they, may their memory be blessed, said (see Mishneh Torah, Laws of Murderer and the Preservation of Life 8:2, 4) [regarding] these six cities that Moshe separated three of them in Transjordan and Yehoshua separated three of them in the Land of Canaan, but the ones of Moshe did not shelter until the three of Yehoshua were separated. And if so, why did Moshe separate them? He said, “[If] a commandment comes to my hand, I will fulfill it.” And at the time of the King Messiah, we will add another three, as it is stated (Deuteronomy 19:9), “and you shall further add for yourself three cities upon these three, etc.” And they, may their memory be blessed, said (Mishneh Torah, Laws of Murderer and the Preservation of Life 8:10) that all of the cities of the Levites would shelter, as it is stated (Numbers 35:6-7), “and upon them you shall give forty-two cities. All of the cities that you shall give to the Levites, etc.” — Scripture compared all of them (the six cities of refuge and the forty-two additional ones). But there is this difference between them — that the cities of refuge shelter, whether knowingly (when the inadvertent killer is seeking refuge there) or not knowingly; whereas the cities of the Levites only shelter knowingly. [Also] a murderer that lives in a city of refuge does not [pay] rent; whereas in the other cities, he [pays] rent. And [also that which] they, may their memory be blessed, said (Bava Batra 100b) that the width of the path [to the] city of refuge is thirty-two ells; and that on the fifteenth of Adar, the court would send agents to fix the paths — and if they were negligent in the matter, it is as if they spilled blood. And [also that which] they, may their memory be blessed, said (Makkot 11b) that the perimeter of any city that shelters, [also] shelters. And the rest of the details of the commandment are in Sanhedrin, in Makkot, in Shekalim and in Sotah.

And this commandment is practiced at the time that Israel is dwelling on their Land. And it is from the commandments incumbent upon the king and upon the whole community.